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Problems in evolutionary psychology

55 Kaj_Sotala 13 August 2010 06:57PM

Note: The primary target of the post is not professional, academic evolutionary psychology. Rather, I am primarily cautioning amateurs (such as LW regulars) about some of the caveats involved in (armchair) evpsych and noting the rigor required for good theories. While the post does also serve as a warning to be cautious about sloppy research (or sloppy science journalism) that doesn't seem to be taking these issues into account, I do believe that most of the researchers doing serious evpsych research are quite aware of these issues.

Evolutionary theories get mentioned a lot on this site, and I frequently feel that they are given far more weight than would be warranted. In particular, evolutionary theories about sex differences seem to get mentioned and appealed to as if they had an iron-cast certainty. People also don't hesitate to make up their own evolutionary psychological explanations. To counterbalance this, I present a list of evolutionary psychology-related problems, divided into four rough categories.

Problems in hypothesis generation

Rationalization bias. We know that human minds are very prone to first deciding on a desired outcome, then coming up with a plausible-sounding story of why it must be so. In general, our minds have difficulty noticing faulty reasoning if it leads to the right conclusion. It's easy and tempting to come up with an ad-hoc evolutionary explanation for any behavior, regardless of whether or not it actually has any biological roots.

Over-attributing meaning. Humans also have a strong tendency to attribute meaning to random chance. We might easily come up with explanations that are unnecessarily complex, and try to make everything into an evolved adaptation. For instance, humans tend to avoid thinking about unpleasant thoughts about themselves. A contrived evpsych explanation might be that this is evolved self-deception: by not acknowledging our own faults, it makes it easier for us to deceive others about them. But mental unpleasantness tends to be correlated with harmful experiences: we avoid situations where we'd be afraid, and fear is correlated with danger. It could just as well be that the mechanism for avoiding mental unpleasantness evolved from the mechanism for avoiding physical unpleasantness, and we avoid thinking unpleasant thoughts of ourselves for the same reason why we avoid poking our fingers at hot stoves. (Example courtesy of Anna Salamon.)

Alternative ways of reaching the goal. Eliezer previously gave us the example of the scientists who thought insects would under the right circumstances limit their breeding, but the insects ended up eating their competitors' offspring instead. We can only cover a limited part of the space of all possible routes evolution could take. While ”but another hypothesis might explain it better” is admittedly a problem all scientific disciplines face, it is especially acute here, since we have very little knowledge of what life in the EEA was actually like.

Problems in background assumptions

Did a genetic path to the adaptation exist? Evolution works by the rule of immediate advantage: for mutation X to reach fixation, it has to provide an immediate advantage. It's well and good to propose that under specific circumstances, organisms that developed a specific behavior would have gained a fitness advantage. But that, by itself, tells us nothing about how many mutations reaching such a behavior would have required. Nor does it tell us anything about whether all of those intermediate stages actually conferred the organism a fitness benefit, making it possible for the final form of the adaptation to actually be reached.

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Forager Anthropology

11 WrongBot 28 July 2010 05:48AM

(This is the second post in a short sequence discussing evidence and arguments presented by Christopher Ryan and Cacilda Jethá's Sex at Dawninspired by the spirit of Kaj_Sotala's recent discussion of What Intelligence Tests MissIt covers Part II: Lust in Paradise and Part III: The Way We Weren't.)

Forager anthropology is a discipline that is easy to abuse. It relies on unreliable first-hand observations of easily misunderstood cultures that are frequently influenced by the presence of modern observers. These cultures are often exterminated or assimilated within decades of their discovery, making it difficult to confirm controversial claims and discoveries. But modern-day foraging societies are the most direct source of evidence we have about our pre-agricultural ancestors; in many ways, they are agriculture's control group, living in conditions substantially similar to the ones under which our species evolved. The standard narrative of human sexual evolution ignores or manipulates the findings of forager anthropology to support its claims, and this is no doubt responsible for much of its confused support.

Steven Pinker is one of the most prominent and well-respected advocates of the standard narrative, both on Less Wrong and elsewhere. Eliezer has referenced him as an authority on evolutionary psychology. One commenter on the first post in this series claimed that Pinker is "the only mainstream academic I'm aware of who visibly demonstrates the full suite of traditional rationalist virtues in essentially all of his writing." Another cited Pinker's claim that 20-60% of hunter-gatherer males were victims of lethal human violence ("murdered") as justification for a Malthusian view of human nature. 

That 20-60% number comes from a claim about war casualties in a 2007 TED talk Pinker gave on "the myth of violence", for which he drew upon several important findings in forager anthropology. (The talk is based on an argument presented in the third chapter of The Blank Slate; there is a text version of the talk available, but it omits the material on forager anthropology that Ryan and Jethá critique.)

At 2:45 in the video Pinker displays a slide which reads

Until 10,000 years ago, humans lived as hunter-gatherers, without permanent settlements or government.

He also points out that modern hunter-gatherers are our best evidence for drawing conclusions about those prehistoric hunter-gatherers; in both these statements he is in accordance with nearly universal historical, anthropological, and archaeological opinion. Pinker's next slide is a chart from The Blank Slate, originally based on the research of Lawrence Keeley. Sort of. It is labeled as "the percentage of male deaths due to warfare," with bars for eight hunter-gatherer societies that range from approximately 15-60%. The problem is that of these eight cultures, zero are migratory hunter-gatherers.

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Against the standard narrative of human sexual evolution

7 WrongBot 23 July 2010 05:28AM

(This post is the beginning of a short sequence discussing evidence and arguments presented by Christopher Ryan and Cacilda Jethá's Sex at Dawn, inspired by the spirit of Kaj_Sotala's recent discussion of What Intelligence Tests Miss. It covers Part I: On the Origin of the Specious.)

Sex at Dawn: The Prehistoric Origins of Modern Sexuality was first brought to my attention by a rhapsodic mention in Dan Savage's advice column, and while it seemed quite relevant to my interests I am generally very skeptical of claims based on evolutionary psychology. I did eventually decide to pick up the book, primarily so that I could raid its bibliography for material for an upcoming post on jealousy management, and secondarily to test my vulnerability to confirmation bias. I succeeded in the first and failed in the second: Sex at Dawn is by leaps and bounds the best evolutionary psychology book I've read, largely because it provides copious evidence for its claims.1 I mention the strength of my opinion as a disclaimer of sorts, so that careful readers may take the appropriate precautions.


The book's first section focuses on the current generally accepted explanation for human sexual evolution, which the authors call "the standard narrative." It's an explanation that should be quite familiar to regular LessWrong readers: men are attracted to fertile-appearing women and try to prevent them from having sex with other men so as to confirm the paternity of their offspring; women are attracted to men who seem like they will be good providers for their children and try to prevent them from forming intimate bonds with other women so as to maintain access to their resources.

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The Psychological Diversity of Mankind

79 Kaj_Sotala 09 May 2010 05:53AM

The dominant belief on this site seems to be in the "psychological unity of mankind". In other words, all of humanity shares the same underlying psychological machinery. Furthermore, that machinery has not had the time to significantly change in the 50,000 or so years that have passed after we started moving out of our ancestral environment.

In The 10,000 Year Explosion, Gregory Cochran and Henry Harpending dispute part of this claim. While they freely admit that we have probably not had enough time to develop new complex adaptations, they emphasize the speed at which minor adaptations can spread throughout populations and have powerful effects. Their basic thesis is that the notion of a psychological unity is most likely false. Different human populations are likely for biological reasons to have slightly different minds, shaped by selection pressures in the specific regions the populations happened to live in. They build support for their claim by:

  • Discussing known cases where selection has led to rapid physiological and psychological changes among animals
  • Discussing known cases where selection has led to physiological changes among humans in the last few thousand years, as well as presenting some less certain hypotheses of this.
  • Postulating selection pressures that would have led to some cognitive abilities to be favored among humans.

In what follows, I will present their case by briefly summarizing the contents of the book. Do note that I've picked the points that I found the most interesting, leaving a lot out.

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Babies and Bunnies: A Caution About Evo-Psych

52 Alicorn 22 February 2010 01:53AM

Daniel Dennett has advanced the opinion that the evolutionary purpose of the cuteness response in humans is to make us respond positively to babies.  This does seem plausible.  Babies are pretty cute, after all.  It's a tempting explanation.

Here is one of the cutest baby pictures I found on a Google search.

And this is a bunny.

Correct me if I'm wrong, but the bunny is about 75,119 times cuter than the baby.

Now, bunnies are not evolutionarily important for humans to like and want to nurture.  In fact, bunnies are edible.  By rights, my evolutionary response to the bunny should be "mmm, needs a sprig of rosemary and thirty minutes on a spit".  But instead, that bunny - and not the baby or any other baby I've seen - strikes the epicenter of my cuteness response, and being more baby-like along any dimension would not improve the bunny.  It would not look better bald.  It would not be improved with little round humanlike ears.  It would not be more precious with thumbs, easier to love if it had no tail, more adorable if it were enlarged to weigh about seven pounds.

If "awwww" is a response designed to make me love human babies and everything else that makes me go "awwww" is a mere side effect of that engineered reaction, it is drastically misaimed.  Other responses for which we have similar evolutionary psychology explanations don't seem badly targeted in this way.  If they miss their supposed objects at all, at least it's not in most people.  (Furries, for instance, exist, but they're not a common variation on human sexual interest - the most generally applicable superstimuli for sexiness look like at-least-superficially healthy, mature humans with prominent human sexual characteristics.)  We've invested enough energy into transforming our food landscape that we can happily eat virtual poison, but that's a departure from the ancestral environment - bunnies?  All natural, every whisker.1

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The Amanda Knox Test: How an Hour on the Internet Beats a Year in the Courtroom

42 komponisto 13 December 2009 04:16AM

Note: The quantitative elements of this post have now been revised significantly.

Followup to: You Be the Jury: Survey on a Current Event

All three of them clearly killed her. The jury clearly believed so as well which strengthens my argument. They spent months examining the case, so the idea that a few minutes of internet research makes [other commenters] certain they're wrong seems laughable

- lordweiner27, commenting on my previous post

The short answer: it's very much like how a few minutes of philosophical reflection trump a few millennia of human cultural tradition.

Wielding the Sword of Bayes -- or for that matter the Razor of Occam -- requires courage and a certain kind of ruthlessness. You have to be willing to cut your way through vast quantities of noise and focus in like a laser on the signal.

But the tools of rationality are extremely powerful if you know how to use them.

Rationality is not easy for humans. Our brains were optimized to arrive at correct conclusions about the world only insofar as that was a necessary byproduct of being optimized to pass the genetic material that made them on to the next generation. If you've been reading Less Wrong for any significant length of time, you probably know this by now. In fact, around here this is almost a banality -- a cached thought. "We get it," you may be tempted to say. "So stop signaling your tribal allegiance to this website and move on to some new, nontrivial meta-insight."

But this is one of those things that truly do bear repeating, over and over again, almost at every opportunity. You really can't hear it enough. It has consequences, you see. The most important of which is: if you only do what feels epistemically "natural" all the time, you're going to be, well, wrong. And probably not just "sooner or later", either. Chances are, you're going to be wrong quite a lot.

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Would Your Real Preferences Please Stand Up?

42 Yvain 08 August 2009 10:57PM

Related to: Cynicism in Ev Psych and Econ

In Finding the Source, a commenter says:

I have begun wondering whether claiming to be victim of 'akrasia' might just be a way of admitting that your real preferences, as revealed in your actions, don't match the preferences you want to signal (believing what you want to signal, even if untrue, makes the signals more effective).

I think I've seen Robin put forth something like this argument [EDIT: Something related, but very different], and TGGP points out that Brian Caplan explicitly believes pretty much the same thing1:

I've previously argued that much - perhaps most - talk about "self-control" problems reflects social desirability bias rather than genuine inner conflict.

Part of the reason why people who spend a lot of time and money on socially disapproved behaviors say they "want to change" is that that's what they're supposed to say.

Think of it this way: A guy loses his wife and kids because he's a drunk. Suppose he sincerely prefers alcohol to his wife and kids. He still probably won't admit it, because people judge a sinner even more harshly if he is unrepentent. The drunk who says "I was such a fool!" gets some pity; the drunk who says "I like Jack Daniels better than my wife and kids" gets horrified looks. And either way, he can keep drinking.

I'll call this the Cynic's Theory of Akrasia, as opposed to the Naive Theory. I used to think it was plausible. Now that I think about it a little more, I find it meaningless. Here's what changed my mind.

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An interesting speed dating study

15 CronoDAS 07 July 2009 07:09AM

I recently found an article in the New York Times that talks about a speed dating study that is going to be published in an upcoming issue of the journal Psychological Science. Given the usual state of science journalism, the fact that the article includes links that let me find a press release about the upcoming paper and a 20-page PDF file containing the paper itself was very helpful.

According to most studies and in accordance with popular stereotypes, men are normally less selective than women when it comes to evaluating potential romantic partners - in general, it appears that men are more likely to want to date any given woman than women are to want to date any given man. In a typical speed dating experiment, men and women rate potential partners as either a "yes" or a "no" depending on whether or not they want to see that person again. Men almost always rate a larger percentage of women as a "yes" than women do men, and, according to this paper, this is a fairly robust finding that generalizes over many different contexts. The usual explanation of this phenomena is based on evolutionary psychology: a female has a lot more to lose from a bad mate choice than a male does. If there were a biological, genetic basis for this tendency, it should be difficult to come up with an experimental setup in which women are less selective and men are more selective.

However, that's not the case at all. This study demonstrates that a small, seemingly trivial change in the speed dating ritual results in a (partial) reversal of the normal results. You see, in practically every speed dating setup, when it is time to interact with a new partner, men physically leave their seat and move to the table where the next woman is sitting, while the women remain seated and wait for the men to approach them. The authors of this study had the men remain still and had the women change seats, and found that this was all it took to wipe away the usual pattern: when the women were required to physically approach while the men remained still, the women became less selective then the men, reporting greater romantic interest and "yes"ing partners at a higher rate. "Rotaters" also reported greater self-confidence than "sitters", regardless of gender.

I suggest that you go read the paper, or at least the press release, yourself; my summary doesn't really do it justice, and I'm leaving the implications for the evolutionary psychology-based analysis of gender as an exercise for the reader.

EDIT: Having had some more time to look over the study, I think I should point out that it wasn't a complete reversal of the usual gender behavior: female rotators were only moderately less selective than male sitters, while male rotators were significantly less selective than female sitters. (Sitters of both genders were equally selective.)

An Especially Elegant Evpsych Experiment

26 Eliezer_Yudkowsky 13 February 2009 02:58PM

Followup toAdaptation-Executers not Fitness-Maximizers, The Evolutionary-Cognitive Boundary

"In a 1989 Canadian study, adults were asked to imagine the death of children of various ages and estimate which deaths would create the greatest sense of loss in a parent. The results, plotted on a graph, show grief growing until just before adolescence and then beginning to drop. When this curve was compared with a curve showing changes in reproductive potential over the life cycle (a pattern calculated from Canadian demographic data), the correlation was fairly strong. But much stronger - nearly perfect, in fact - was the correlation between the grief curves of these modern Canadians and the reproductive-potential curve of a hunter-gatherer people, the !Kung of Africa. In other words, the pattern of changing grief was almost exactly what a Darwinian would predict, given demographic realities in the ancestral environment...  The first correlation was .64, the second an extremely high .92."

(Robert Wright, summarizing:  "Human Grief:  Is Its Intensity Related to the Reproductive Value of the Deceased?"  Crawford, C. B., Salter, B. E., and Lang, K.L.  Ethology and Sociobiology 10:297-307.)

Disclaimer:  I haven't read this paper because it (a) isn't online and (b) is not specifically relevant to my actual real job.  But going on the given description, it seems like a reasonably awesome experiment.  [Gated version here, thanks Benja Fallenstein.  Odd, I thought I searched for that.  Reading now... seems to check out on the basics.  Correlations are as described, N=221.]

The most obvious inelegance of this study, as described, is that it was conducted by asking human adults to imagine parental grief, rather than asking real parents with children of particular ages.  (Presumably that would have cost more / allowed fewer subjects.)  However, my understanding is that the results here squared well with the data from closer studies of parental grief that were looking for other correlations (i.e., a raw correlation between parental grief and child age).

That said, consider some of this experiment's elegant aspects:

  • A correlation of .92(!)  This may sound suspiciously high - could evolution really do such exact fine-tuning? - until you realize that this selection pressure was not only great enough to fine-tune parental grief, but, in fact, carve it out of existence from scratch in the first place.
  • People who say that evolutionary psychology hasn't made any advance predictions are (ironically) mere victims of "no one knows what science doesn't know" syndrome.  You wouldn't even think of this as an experiment to be performed if not for evolutionary psychology.
  • The experiment illustrates as beautifully and as cleanly as any I have ever seen, the distinction between a conscious or subconscious ulterior motive and an executing adaptation with no realtime sensitivity to the original selection pressure that created it.

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The Evolutionary-Cognitive Boundary

22 Eliezer_Yudkowsky 12 February 2009 04:44PM

I tend to draw a very sharp line between anything that happens inside a brain and anything that happened in evolutionary history.  There are good reasons for this!  Anything originally computed in a brain can be expected to be recomputed, on the fly, in response to changing circumstances.

Consider, for example, the hypothesis that managers behave rudely toward subordinates "to signal their higher status".  This hypothesis then has two natural subdivisions:

If rudeness is an executing adaptation as such - something historically linked to the fact it signaled high status, but not psychologically linked to status drives - then we might experiment and find that, say, the rudeness of high-status men to lower-status men depended on the number of desirable women watching, but that they weren't aware of this fact.  Or maybe that people are just as rude when posting completely anonymously on the Internet (or more rude; they can now indulge their adapted penchant to be rude without worrying about the now-nonexistent reputational consequences).

If rudeness is a conscious or subconscious strategy to signal high status (which is itself a universal adapted desire), then we're more likely to expect the style of rudeness to be culturally variable, like clothes or jewelry; different kinds of rudeness will send different signals in different places.  People will be most likely to be rude (in the culturally indicated fashion) in front of those whom they have the greatest psychological desire to impress with their own high status.

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